Suitably designed electrochemiluminescence (ECL) carrying group acting as high-efficiency solid-state probe has attracted a lot of attention. Herein, molybdenum carbides with the two-dimensional ultrathin nanosheet structure on the surface and excellent conductivity were successfully employed as the nanocarriers for the capture of ECL reagent of luminol-capped Au nanoparticles (luminol-AuNPs). Notably, the luminol-AuNPs in the hybrid (luminol-AuNPs@Mo2C) exhibited enhanced ECL performance (∼6-fold) as compared to individual luminol-AuNPs because of the facilitated electron transfer process. Ultimately, the as-prepared ECL label was used to construct a label-free ECL immunosensor for the detection of α-fetoprotein (AFP). The immunosensor shows high selectivity and high sensitivity to AFP detection with a wide linear range of 0.1 pg·mL–1 to 30 ng·mL–1 and an extremely low detection limit of 0.03 pg·mL–1 (S/N = 3). Moreover, the fabricated ECL immunosensor exhibit satisfied performance in the practical application. This novel sensing strategy not only broadens the application of molybdenum carbides but also provides a new efficient approach to detect various biomolecules.

A bipolar electrode (BPE) is an electron conductor that is embedded in the electrolyte solution without the direct connection with the external power source (driving electrode). When the sufficient voltage was provided, the two poles of BPE promote different oxidation and reduction reactions. During the past few years, BPEs with wireless feature and easy integration showed great promise in the various fields including asymmetric modification/synthesis, motion control, targets enrichment/separation, and chemical sensing/biosensing combined with the quantitative relationship between two poles of BPE. In this perspective paper, we first describe the concept and history of the BPE for analytical chemistry and then review the recent developments in the application of BPEs for sensing with ultrahigh current efficiency (ηc = iBPE/ichannel) including the open and closed bipolar system. Finally, we offer the guide for possible challenge faced and solution in the future.Keywords: bipolar electrode; chemical sensing/biosensing; closed bipolar system; high current efficiency; open bipolar system;

Bimetallic nanoclusters (NCs) with superior performance to that of monometallic nanoclusters have attracted extensive research interest due to the synergetic effect of the two atoms. Inspired from the silver effect on the enhanced fluorescence intensity of Au NCs, a series of bovine serum albumin-protected Au–Ag bimetallic NCs were prepared by regulating the molar ratios of HAuCl4/AgNO3 and their electrochemiluminescence (ECL) property was investigated using triethylamine as co-reactant. Notably, multifold higher efficiency was achieved with Au–Ag bimetallic NCs in reference to the monometallic nanoclusters. Moreover, the doping of Ag atoms not only made the ECL emission of the Au NCs blue shift but also decreased the peak potential and onset potential, which provided an efficient and facile way to improve the ECL behavior. Based on the ECL quenching effect of Hg2+ toward Au–Ag bimetallic NCs via the formation of metallophilic bond, an ECL sensor for Hg2+ detection was proposed with good stability and high selectivity and sensitivity. These results indicated that the as-prepared Au–Ag bimetallic NCs with enhanced ECL properties can be served as an ideal luminescent material in sensing application.

A facile, green and versatile method has been developed to prepare MoSe2 nanodots through polyvinylpyrrolidone (PVP)-assisted liquid phase exfoliation. The obtained nanodots showed a narrow size and thickness distribution. Moreover, these ultrasmall MoSe2–PVP nanocomposites could serve as efficient light-absorbing agent for photothermal therapy with negligible cell toxicity and appreciable photothermal effect.

We report a simple, low-cost, and brand-new electrochemical lithography technique for replicating the template pattern with high resolution at ∼2 μm. The developed method is that the electroactive material is first deposited on the patterned conductive template by the electrochemical technique and then peeled by an adhesive tape/material. The resulting film with the precise pattern shows excellent mechanical and electronic properties and promises high prospect in designing flexible electronics. This interesting approach can be performed at ambient conditions and easily generalized to pattern various electroactive materials covering metal, alloy, nonmetal, salt, oxide, and composite on different types of substrates in several seconds to a few minutes, making the mass production of flexible/rigid/stretchable patterned thin films quite possible.

The direct growth of Mo, S-codoped NiSe nanosheet assemblies on nickel foam (Mo, S-codoped NiSe/NF-160 NSs) was fulfilled through a one-step hydrothermal reaction, which exhibited enhanced HER activity delivering a current density of 10 mA cm−2 at an overpotential of 88 mV, a small Tafel slope of 82 mV dec−1 and excellent stability in an alkaline electrolyte.

Herein, a multifunctional nanoarchitecture has been developed by integrating well-crystalline molybdenum carbide (Mo2C) nanotubes and an electrochemical indicator – thionin (TH). The Mo2C nanotubes were synthesized through the self-degradable template method and high-temperature calcination, and their structure and morphology were characterized through scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Due to the high electrocatalytic properties, excellent conductivity and highly active surface area of Mo2C nanotubes, the Mo2C-based material was used as a nanocarrier to load TH molecules for the development of a label-free electrochemical immunosensor for α-fetoprotein (AFP) detection. The decorated TH probe on the Mo2C nanotubes not only acted as a bridging molecule to effectively capture and immobilize primary anti-AFP on the Mo2C nanotubes, but also acted as a signal indicator for the detection of AFP. The proposed immunosensor exhibited excellent selectivity (with a detection limit of 3 pg mL−1), high stability and good reproducibility by combining the unique structure and features of the Mo2C nanotubes. Furthermore, this sensing platform was finally used for the detection of AFP in human serum with satisfactory results. Therefore, the Mo2C nanotubes can be considered as a candidate carbon material for fabrication of simple, label-free and ultrasensitive electrochemical sensors, broadening the application of this material.

In this work, we report a nanoscale multichannel closed bipolar electrode (BPE) array based on the poly(ethylene terephthalate) (PET) membrane for the first time. With our design, oxidants, coreactants, quenchers, and even biomarkers can be detected in a Ru(bpy)32+/TPA (tripropylamine) electrochemiluminescence (ECL) system. The multichannel PET membrane was etched according to our desire by NaOH, and then Au nanofibers were decorated in the inner region of the channel as a BPE array. Using ECL as a signal readout, a series of targets including TPA, Ru(bpy)32+, dopamine, H2O2, alpha-fetoprotein (AFP), and carcino-embryonic antigen (CEA) can be detected with this device. The practical application of the proposed multichannel closed BPE array was verified in the detection of AFP and CEA in human serum with satisfying results. This kind of nanoscale device holds promising potential for multianalysis. More importantly, as the PET membrane used in this device can be etched with a desirable diameter (nano- to microscale) and different BPE array densities (ion tracks of 108/cm2, 106/cm2, 104/cm2), our design can be served as a useful platform for future advances in nanoscale bipolar electrochemistry.

Here we report a self-powered-bipolar-electrochromic-electrode (termed SP-BP-EC-E) array for the displaying applications including catalyst screening, catalytic activity measurement, and enzyme substrate quantification. By replacing the directional (or active) power source with the isotropic chemical energy to drive the bipolar electrochemical reaction, the driving background signal, bipolar electrode (BPE) background signal, uneven reporting signal and the influence of electrolysis which commonly appear in traditional bipolar systems are effectively eliminated from origin. Thus, the reporting signals from the SP-BP-EC-E arrays can be more direct and reliable to reflect the target nature. Such a SP-BP-EC-E platform exhibits a sensitive response toward the fast analysis of commercial Pt black catalyst, NiPdAu hollow nanospheres, glucose dehydrogenase, and glucose. To our knowledge, this test paper-like SP-BP-EC-E is the simplest platform for high-throughput screening to date, which offers a very convenient approach for nonprofessional people to access the complicated screening and fast analysis of the electrocatalysts and biocatalyst activity and quantification of enzymatic substrates.

Correction for ‘Electrochromic sensing platform based on steric hindrance effects for CEA detection’ by Qingfeng Zhai et al., Analyst, 2016, DOI: 10.1039/c6an00675b.

In this work, an electrochromic sensing platform with prussian blue (PB) as the indicator was proposed for signaling carcinoembryonic antigen (CEA) using the bipolar electrode (BPE) system. The CEA aptamer was pre-anchored on the anode pole of the BPE for capturing CEA through strong binding affinity. The presence of CEA induced the increase of steric hindrance and led to lower electrochemical currents. Due to the quantitative relationship between the two reactions occurring at both ends of the BPE, the amount of deposited PB in situ can be used as an indicator for reporting target protein concentration. Using CEA concentration in normal human serum as a reference (5 ng mL−1), this electrochromic sensing platform can be used for distinguishing persons with cancer from normal humans easily and quickly, which is very important for subsequent treatment of patients. This novel electrochromic platform has great selectivity for target tumor proteins and provides a fast, visual method for CEA detection. Finally, the proposed biosensor can be applied to detect CEA in human serum, which holds great potential for point-of-care diagnostics combined with the advantage of the closed BPE system.

•Bipolar electrode sensing mechanism for conductivity was proposed.•ECL conductivity sensor: flexible linear range and detection limit.•A low-cost, simple, portable and disposable sensing device was fabricated.Here we report a new conductivity sensing mechanism using a closed bipolar electrode (BPE) system for the first time. Briefly, the voltage dropping across the ECL reporting cell will change with the sample conductivity of the analytes cell in a closed bipolar system. Thus, a quantitative relation between the electrochemiluminescence (ECL) response and the sample conductivity is established. Based on this principle, chemicals those are not electroactive materials and do not participate in the ECL process can be detected now, which greatly expands the application range of the BPE and the powerful ECL technique. Then a paper-based bipolar ECL conductivity sensing platform was constructed and carefully characterized, and the results proved the rationality of this newly-proposed bipolar conductivity sensing mechanism. More importantly, this design is also a universal sensing platform, suitable for all the electrolytes without electroactivity (newly proposed), electroactive chemicals and chemicals directly related to the ECL reaction.

A highly active electrocatalyst in the whole pH range for oxygen reduction reaction (ORR) is produced by employing the g-C3N4 assisted metal–organic frameworks (MOF) of C3N4@NH2-MIL-101 as the precursor. By pyrolyzing the hybrid at 700 °C, the C3N4@NH2-MIL-101 could be easily transformed into an abundant iron and nitrogen codoped porous carbon skeleton. The selective use of g-C3N4 as a support template plays a critical role in facilitating the formation of the architecture with high surface area and rich N content. The obtained catalyst of C3N4@NH2-MIL-101-700 manifested remarkable oxygen reduction activity over the pH 0–14. Noteworthy, the catalyst displayed outstanding ORR activity with more positive half-wave potential than that of the commercial Pt/C catalyst in both alkaline and neutral conditions. Additionally, the optimal C3N4@NH2-MIL-101-700 also exhibited prominent ORR activity which is almost equal to that of commercial Pt/C in acidic electrolyte with high selectivity and very low H2O2 yield. Most importantly, the better methanol tolerance and much higher stability than the commercial Pt/C of C3N4@NH2-MIL-101-700 no matter under alkaline, neutral, or acid conditions further demonstrate the catalyst to be a promising candidate for practical electrocatalytic applications.Keywords: electrocatalysts; g-C3N4; metal−organic frameworks; oxygen reduction reaction; porous materials;

Herein, branched poly-(ethylenimine) functionalized graphene/iron oxide hybrid (termed as BGNs/Fe3O4) was chosen as an efficient support material to load AuPt alloy nanoparticles for constructing a multifunctional nanocatalyst via a simple and controlled self-assembly approach. BGNs/Fe3O4 as a nanocarrier made the AuPt alloy nanoparticles uniformly distributed on the surface of BGNs/Fe3O4. The obtained multifunctional nanocatalyst was characterized by high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) spectroscopy, UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The nanocatalyst exhibited favorable water solubility, excellent dispersion, good stability, superparamagnetism and particularly high catalytic activity for reducing 4-nitrophenol (4-NP). Furthermore, by tuning the composition of the nanoalloy nanoparticles of the multifunctional nanocatalyst, a normalized rate constant of about 17.99 mg−1 s−1 was achieved, which was superior to most of the Au or Pt based nanocatalysts reported in recent years. In addition, it was proved that the magnetic Fe3O4 nanoparticles not only ensured the reuse of the nanocatalyst, but also significantly improved the catalytic activity. Thanks to the favorable catalytic activity, the obtained multifunctional nanocatalyst may hold great potential for various catalytic processes.

A universal method for electrodeposition of various materials onto an indium tin oxide (ITO) coated substrate with high mechanical stability, which solves one of the most important problems concerning the modified ITO electrodes in practical applications, is presented.

Here we report a novel sensing strategy based on the closed bipolar system, in which we utilize a light emitting diode (LED) to connect a split bipolar electrode (BPE) and generate the luminescent signal in the presence of the target. With this design, we have constructed a BPE array for the quick and high-throughput determination of various electroactive substances with naked eyes. Due to the ultrahigh current efficiency of the closed bipolar system, the sample concentration can be reported by the luminous intensity of the inserted LED without the expensive luminescent agent and instruments. Besides, the stability of the signal is improved because of the electroluminescent property of the LED. To demonstrate the promising applications of the bipolar LED electrode (BP-LED-E), the rapid quantification of four model targets (H2O2, ascorbic acid (AA), glucose, and blood sugar) has been achieved based on different principles.

In this work, a sensitive and selective ratiometric fluorescence sensing platform was built for the detection of tyrosinase (TYR) activity and dopamine (DA) using glutathione (GSH) protected gold nanoclusters (Au NCs) as probes. Upon excitation at 350 nm, Au NCs displayed an intense red emission, which could be effectively quenched by quinones. TYR, a typical polyphenol oxidase, can catalyze the oxidization of DA to o-quinone and therefore quenched the fluorescence of Au NCs. Moreover, the reaction of TYR and DA gave rise to an emission band at 400 nm, which increased in a TYR/DA-concentration-dependent manner. The ratiometric signal variations were utilized for facile, sensitive, and selective detection of TYR activity and DA. A linear range was obtained from 0.006–3.6 unit mL–1 of TYR activity, while the linear range for detection of DA was 1.0 nM to 1.0 mM. Additionally, it constructed a useful platform for TYR inhibitor screening in biomedical research.

Herein, a multifunctional nanoarchitecture has been developed by integrating the branched poly(ethylenimine) functionalized graphene/iron oxide hybrids (BGNs/Fe3O4) and luminol capped gold nanoparticles (luminol-AuNPs). The luminescent luminol-AuNPs as an electrochemiluminescence marker can be assembled on the nanocarrier of BGNs/Fe3O4 hybrids efficiently via the Au–N chemical bonds and electrostatic adsorption. Meanwhile, the multifunctional nanoarchitecture has been proved with excellent electron transfer, good stability, high emission intensity, etc. Furthermore, we successfully developed an ultrasensitive magnetically-controlled solid-state electrochemiluminescence (ECL) platform for label-free determination of HeLa cells using this multifunctional nanocomposite. Excellent performance of the magnetically-controlled ECL biosensing platform has been achieved including a high sensitivity for HeLa cells with a linear range from 20 to 1 × 104 cells/mL, good stability, and reproducibility.

A facile, green and versatile method has been developed to prepare MoSe2 nanodots through polyvinylpyrrolidone (PVP)-assisted liquid phase exfoliation. The obtained nanodots showed a narrow size and thickness distribution. Moreover, these ultrasmall MoSe2–PVP nanocomposites could serve as efficient light-absorbing agent for photothermal therapy with negligible cell toxicity and appreciable photothermal effect.

A universal method for electrodeposition of various materials onto an indium tin oxide (ITO) coated substrate with high mechanical stability, which solves one of the most important problems concerning the modified ITO electrodes in practical applications, is presented.

Herein, branched poly-(ethylenimine) functionalized graphene/iron oxide hybrid (termed as BGNs/Fe3O4) was chosen as an efficient support material to load AuPt alloy nanoparticles for constructing a multifunctional nanocatalyst via a simple and controlled self-assembly approach. BGNs/Fe3O4 as a nanocarrier made the AuPt alloy nanoparticles uniformly distributed on the surface of BGNs/Fe3O4. The obtained multifunctional nanocatalyst was characterized by high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) spectroscopy, UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The nanocatalyst exhibited favorable water solubility, excellent dispersion, good stability, superparamagnetism and particularly high catalytic activity for reducing 4-nitrophenol (4-NP). Furthermore, by tuning the composition of the nanoalloy nanoparticles of the multifunctional nanocatalyst, a normalized rate constant of about 17.99 mg−1 s−1 was achieved, which was superior to most of the Au or Pt based nanocatalysts reported in recent years. In addition, it was proved that the magnetic Fe3O4 nanoparticles not only ensured the reuse of the nanocatalyst, but also significantly improved the catalytic activity. Thanks to the favorable catalytic activity, the obtained multifunctional nanocatalyst may hold great potential for various catalytic processes.